The present invention relates to an apparatus for the drying of solutions, dispersions and suspensions on a heatable internal surface containing a rotatable fitting, a feed device, a discharge device for dried product and a vapour outlet.
Thin layer apparatus are known in which rigidly fixed rotor edges on the thin layer evaporator proper are replaced by edges which are rotatably fixed to hinges. The minimum gap between the wall and the pendulous edges is 0.3 to 0.5 mm. This can be used to adjust a thin layer on the inside of a cylindrical pipe, and such a thin layer evaporator can therefore also be used as thin layer drier. Liquids which are capable of being pumped can in this way be continuously processed in a thin layer apparatus to be converted into loose pourable solid material in a single step.
Unfortunately, however, many products cannot be dried continuously in this manner because they often pass through a viscous state in the course of drying so that they stick to the internal wall and form incrustations on the elements provided for stripping the wall so that these elements cease to be sufficiently mobile and fail to function as stripping elements. The least harmful result is that a lumpy product is obtained but in most cases the drier breaks down within a short time and must be cleaned by a complicated and difficult process.